Analysis of the Blood Level Group and Full IQ Score

Analysisof the Blood Level Group and Full IQ Score

Astudy was conducted to determine the relationship between their levelof IQ and the level of lead in their blood. The meta-analysis wasconducted on a sample group 121 school-going children. The size ofthe effect of lead was emphasized to allow for an informedcomparison. The main objective of the research was to find theassociation between the level of lead in the blood of children andtheir IQ score. 121 children with different blood lead levels 1, 2,and 3 were tested for their IQ levels and the results recorded on atable. The primary aim of this article is to discover how the levelof lead in the blood affected the IQ of the children in the study.

Thetotal group consisted of 121 children, of whom 78 had blood levelgroup one, 22 had blood level group two and 21 had blood level group3. Below is a pie chart representing the information above

Thewhole sample group

Outof the 121 children tested, the highest IQ score recorded was 141while the least IQ score recorded was 46. The highest score was froma 15 year old person with a blood lead level of 2 while the leastscore was from a 7 year old with a blood lead level of 2. The medianIQ score for the whole group was 90 while the modal IQ score wasrecorded at 96.

MeanIQ score

Themean score of the whole group is the average between the 121 studentscan be calculated by dividing the total IQF score and the totalnumber:

TotalIQ score: 10989.

Totalnumber: 121

MeanIQF score = 10989/121 = 90.81818

Thismeans that the average IQ score for the whole group regardless of theblood level group was 90.818.


Thevariance for the whole sample group can be calculated by:

Variance= Variance= 187.1315

TheStandard deviation

Thestandard deviation of the whole sample group can be calculated by

Standarddeviation =

=13.6796 13.68

BloodLead Level Group One

Therewere 78 people with blood lead level group one. The highest IQ scorefor this level was 141 while the least IQ score was 51. The mean IQscore is the average score between the 78 children. It can be gottenby dividing the sum total IQ score and the total number of children.

TotalIQ score: 7245. Total number of children = 78

Meanscore = 7245/78 = 92.88462

Theaverage IQF score for the blood lead level group one was 92.885


Themodal score is the IQF score that appears the most often. For thepeople with blood level group one, the modal score appears to be 96.


Thevariance is calculated by getting the squared difference from themean then getting the average. The variance is given by:

Thesum of squared difference = 18129.93

Thetotal number of children = 78

Thevariance =

Variance= 235.4536

TheStandard deviation

It is given by the square root of the variance and is a measure of hownumbers are spread out. It is symbolized by the Greek letter sigma(σ). Theformula is given by:



BloodLead Level 2 Group

Therewere 22 children with the blood lead level 2 group this composedabout 18.18% of the total sample group. They had a mean total scoreof 87.227 in IQF score.The highest IQ score was 114 while theleast IQ score in the group was 46. It was this group that recordedtheir least IQF score for the entire sample group. The average score=


Themodal score for this group was recorded at 91 while the median was90.5.


Thevariance for the blood lead level 2 group can be given by




Thestandard deviation of the group can be gotten by getting the squareroot of the group’s standard deviation.

Std.deviation =


Bloodlead level 3 Group.

Outof the 121 sampled groups, 21 children had the blood lead level 3 andhad a modal score of 80 IQF points. They also recorded a median scoreof 85 IQF points. The group recorded a high score of 104 IQF pointsand the least score of 75 IQF score.


Theaverage score of the group can be gotten by


Themodal score for the group was 80 points while the median score was 85IQF.


Thegroup’s variance is given by the formula




Thestandard deviation is given by the square root of the variance. Theformula is given by


Belowis a frequency table showing the distribution of the scores.



Cumulative frequency

A: 0.00 – 19.0



B: 20.0 – 39.0



C: 40.0– 59.0



D: 60.0 – 79.0



E: 80.0 – 99.0



F: 100.0–119.0









Plottinga frequency bar graph to illustrate the above information:

Thenull hypothesis:

Thehypothesis of this test is that the level of lead in the blood willhave no impacts on the IQ value the IQ of a person can only beaffected by age and nurture.


Thenull hypothesis is false, and that the lead level in the blood willdrastically affect the IQ value of an individual.

Thususing the p-value approach, if the p-value equals or less than the=0.05, we reject the null hypothesis, and accept the alternativehypothesis. However, if the p-value is greater or equals α= 0.05,then the null hypothesis is accepted, and the alternative hypothesisis rejected.

Assumingthe null hypothesis is true, we conduct the test for the hypothesiswith the population mean. Using the t-statistic, we find thet-distribution with the degree of freedom as n-1.

Theformula is given by t* =(x-u)/(8/√n).

Thuscalculating the confidence intervals, we find that 90% confidenceinterval extends from 103.49-140.72

The95% confidence intervals extend from 100.40 to 144.58 while the 99%interval extends from 94.55 to 152.33. Since the margin of making aType 1 error is only 5%, thus the confidence interval is 95%. Thismeans that the p-value is less than or equals α= 0.05. Therefore, wereject the null hypothesis and accept the alternative hypothesis.Therefore, it is true that the level of lead in the blood of anindividual will affect the IQ score.

Inconclusion, there was a significant relationship between the exposureof lead to children and their level of IQ. A rise in blood lead levelin the children was linked to a decrease in the IQ scores of thechildren. It has been found that lead interferes withneurotransmission because they bind to the receptors in the neurons.This leads to the inhibition of long-term potentiating of thehippocampal brain region (Schwartz, 1994).


J,S. (2016). Low-levellead exposure and children`s IQ: a meta-analysis and search for athreshold. – PubMed – 20 April 2016, from

Lanphear,B., Hornung, R., Khoury, J., Yolton, K., Baghurst, P., &ampBellinger, D. et al. (2005). Low-Level Environmental Lead Exposureand Children’s Intellectual Function: An International PooledAnalysis. EnvironHealth Perspect,113(7),894-899.